Here's a departure from your normal 3d screenshots. Here's an effect I
thought up the other night and hadn't recalled seeing before. It allows
for a smooth melting/dissolving (kind of hard to describe) of an image.

It's really pretty simple. First you draw the background image (or
clear the buffer if you're fading to black). Then you need an alpha
texture with a nice gradient (middle picture) which describes the effect
you want. You render this solely to the depth buffer with alpha testing
on and some number for the vertex alpha (the number will increase or
decrease each frame). Then you slap the texture being melted on top of
that with a depth test on. If you want to get fancy, you can do what
I've done here and do a slightly different alpha test on top of that to
get nice little borders around the holes you've made.

Also, though I don't have shots of it here, you could use different
alpha textures to get some different effects. Screen wipes or dissolves
(see your favorite Star Wars movie for examples) are easy, though you
really want the highest possible alpha depth for your texture on
something like that. The background also doesn't have to be a single
texture, it could be an entire scene. The engine I'm working on
currently has a console that "melts in" when you open it, though I'll
probably be tired of that soon enough. :)

If you've got any questions/thoughts/whatever feel free to post a
comment.